It was impossible to verify either claim. Koang's claims in the past have been wildly exaggerated, but military and government death tolls announced to the public have also sometimes been underreported.

Aguer denied that Koang's claims were true.

The recent massacre in Bentiu has alarmed the international community, with the U.N. Security Council expressing "horror" and deploring the use of radio broadcasts to "foment hate and sexual violence" in the attack.

U.S. Secretary of State John Kerry on Saturday spoke with the president of South Sudan, Salva Kiir, "to express grave concern" about the violence and the targeting of civilians by both military and rebel forces, a State Department statement said.

The statement also said Kerry denounced recent attacks on U.N. bases and personnel in South Sudan.

Copyright 2014 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.